Carburettors



C. SHORROCK Aug. 8, 1967 CARBURETTORS Filed Feb. 28, 1966 In lien for C192/3 roPh'fie S/QWAKOC'K A ttorneys United States Patent ABSTRACT OFTHE DISCLOSURE A mixing chamber of a carburetor having a rectangularsection portion, on opposite walls of which are pivoted two plateshaving their facing faces curved, the plates being synchronouslyadjustable from an open position where they lie along their respectivewalls to a position with their tips closed together at, or near, anddownstream of a main jet and a compensating jet debouc'hing into thechamber, the facing faces being curved to assist in directing any fluidflow between the plates with a minimum of turbulence.

This invention concerns improvements relating to carburettors forinternal combustion engines.

By the term mixing chamber is meant the part of the carburettor .inwhich air and fuel mix to provide the airfuel mixture before passinginto the inlet manifold of the internal combustion engine, the fuelpassing into the mixing chamber by means of a main jet and acompensating jet as is normal.

By the term throttle valve used herein is meant a device intended topermit controlled and variable restriction of the through orifice of aconduit, within which the valve is mounted, to permit control of thequantitative flow of fluid through the conduit.

By the term butterfly valve used herein is meant a known type ofthrottle valve which comprises a disc or plate which is complementary toand a close fit within the orifice of the conduit. This disc or plate ispivoted centrally about an axis at right angles to the through axis ofthe orifice to be pivotal through an angle of approximately 90 betweenlimit positions in which it closes and opens the orifice.

According to the present invention there is provided a mixing chamberfor a carburettor, the main and compensating jets being spaced axiallyfrom one another along a plane extending longitudinally within andbisecting the chamber.

Preferably the compensating jet is located downstream of the main jet.

Preferably also a throttle valve is provided in the mixing chamber, thethrottle valve including two plates, the plates being pivotally attachedto opposed walls of a portion of the mixing chamber rectangular insection, and means for pivoting said two plates in synchronism with oneanother to move them from a first or open position in which each platelies along the respective wall of the rectangular section portion towhich it is pivotally attached, to a second position in which thedownstream tips of the plates are closed together just downstream of oneof the main and compensating jets.

Preferably the facing faces of the plates are curved to assist indirecting any flow of fluid between the two plates with the minimumturbulence.

Preferably also each plate is pivotally attached at its upstream end tothe respective wall of the rectangular section portion.

Preferably, further, the plates are pivotally attached within recessesin the inside walls and the outside faces 3,334,876 Patented Aug. 8,1967 of the plates are fiat to enable them to lie against the respectiveinside walls.

A second throttle valve may be provided in the mixing chamber, thissecond valve comprising a butterfly valve, which is operated from anoutside source such as a throttle pedal or control lever, movement ofthe butterfly valve being followed by a cam and a cam roller connectedto said means for pivoting the two plates of the first valve, the cambeing suitably profiled so as always to open or shut the plates of thefirst valve an amount in proportion to the movement of the butterflyvalve.

Preferably the second valve is located downstream of the first valve,and the cam profile is chosen so that fluid flow through the first andsecond valves is at a constant velocity.

In an embodiment of the present invention illustrated in theaccompanying drawing which is a sectional elevation through the mixingchamber, a first throttle valve is mounted in a rectangular, for examplesquare, section 10 of the mixing chamber. The moving parts of the 'valvecomprise two specially shaped plates 11, 12 of a suitable metal or othermaterial, which are mounted on opposed walls 13, 14 inside the chamber,one plate 11 on the top inside wall 13 and the other plate 12 on thebottom inside wall 14. This pivotal mounting is achieved by mounting theupstream ends of the plates on pivot pins 15, 16 located in recesses 31,32 in the top and bottom inside walls, 13 and 14 respectively, so thatin one extreme position of pivotal movement the plates may lie along therespective walls, the appropriate face 17, 18 of each plate being flatto enable it to lie against the respective inside wall.

The inside or facing faces 19, 20 of the two plates are curved to assistin directing any flow of fuel-air mixture through the mixing chamberbetween the two plates with the minimum turbulence imparted to thismixture which will be emitted past the plates in a steady stream passingcentrally through the chamber.

The two plates 11, 12 have to pivot towards or away from one another insynchronism so that the downstream tips 21, 22 of the two plates, whicheach described an are when the plates are pivoted between their extremepositions, will always be at the same distance from a horizontal planedisecting the mixing chamber. This synchronised movement of the twoplates can be achieved through various drive arrangements, for example,the

two pivot pins 15, 16 mounting the plates, can be geared to a commonrack, (not shown) and the rack and the pivot pins can be so gearedtogether that movement of the rack in one direction will impart thedesired movement, through the pivot pins, to the plates. As analternative example, the two pivot pins could be connected to thecentres of equi-sized separate meshing gear segments. Movement impartedto one segment in one rotational direction will cause equal but oppositerotational movement of the other segment.

The drive arrangement for pivoting the two plates is, of course,actuated by and under the control of the throttle pedal in the case of amotor vehicle.

The carburettor in which the throttle is provided has two fuel jets, amain jet and a compensating jet, debouching through two emulsion tubes23, 24 into the mixing chamber through a side wall thereof, the twoemulsion tubes being spaced apart but centred upon the aforesaidhorizontal plane bisecting the mixing chamber, the compensating jett-ube 24, being down-stream of the main jet tube 23 but just upstream ofthe tips 21, 22 of the two mixing chamber by the main air flow overthese tubes through the mixing chamber.

The interfunction of jets 24 and 23, with regard to discharge of fueltherefrom, is a basic and important consideration and is only achievedby the design of the venturi throat. For starting and slow running,maximum depression is achieved on the compensating jet 24, thisdepression continuing with progressively diminishing effect untildepression is obtained, due to an increased throttle opening, on bothjets 24 and 23. Further opening, of the throttle decreases thedepression on jet 24, at which point jet 23 takes over, after whichthere is no or very little discharge from jet 24. It is by means of thelocation of the two jets in relation to the venturi throat thatprogressive mixture control is to a large extent dependent.

A second throttle valve is provided in the mixing chamber downstream ofthe first valve, this second valve comprising a butterfly valve 25, theoperation of which is controlled from an outside source such as .athrottle pedal or control lever 33, movement of the butterfly valvebeing followed by a cam 26 and a cam roller 27. The cam roller isconnected by a mechanical linkages 28, 29, 30, to the arrangement forpivoting the plates of the first valve, whereby pivotal movement of thebutterfly valve 25 is transmitted to the cam 26 which through the camroller 27 and the linkage 28, 29 30, opens or closes the plates 11, 12of the first valve an amount in proportion to the extent of pivotalmovement of the butterfly valve. The cam is suitably profiled so thatfluid flow through the plate and butterfly valves is at a constantvelocity in order to minimise any turbulence imparted to the fuel-airmixture flowing through the mixing chamber when the butterfly valvemoves.

One reason for the provision of the second or butterfly valve 25, inaddition to the first valve is that without the second valve and withthe plates 11, 12 of the first valve in the closed position or closetogether, a load would be imposed on these plates trying to open them,the imposition of this load being due to the high vacuum or negativepressure existent in the engine inlet manifold under small openings ofthe valve. With the addition of the butterfly valve, the negativepressure acting upon the plates of the first valve will be controlled bythe relative opening of the butterfly valve which itself is in pneumaticbalance as it is pivoted about its centre.

I claim:

1. A mixing chamber of a carburettor having a main jet and acompensating jet for the supply of combustion fuel, spaced from oneanother with their axes lying in a single plane extending longitudinallywithin and bisecting the chamber, the compensating jet being locateddownstream of the main jet, and having a throttle valve comprising twopl-ates pivotally attached to opposed walls of a portion of the mixingchamber rectangular in section, means being provided for pivoting saidtwo plates in synchronism with one another to move them from a first oropen position in which each plate lies along the respective wall of therectangular section portion to which it is pivotally attached, to asecond position in. which the downstream tips of the plates are closedtogether just downstream of the compensating jet, and wherein the facingfaces of the plates are curved to assist in directing any flow of fluidbetween the two plates with a mini mum of turbulence.

2. A mixing chamber as claimed in claim 1 in which each plate ispivotally attached at its upstream end to the respective wall of therectangular section portion.

3. A mixing chamber as claimed in claim 1 in Which the plates arepivotally attached within recesses in the inside walls and the outsidefaces of the plates are flat to enable them to lie against therespective inside walls.

4. A mixing chamber as claimed in claim 1 in which a second throttlevalve is provided, this second valve comprising a butterfly valve, whichis operated from an outside source such as a throttle pedal or controllever, movement of the butterfly valve being followed by a cam and a camroller connected to said means for pivoting the two plates of the firstvalve, the cam being suitably profiled so as always to open or shut theplates of the first valve an amount in proportion to the movement of thebutterfly valve.

5. A mixing chamber as claimed in claim 4 in which the second valve islocated downstream of the first valve,

and the cam profile is chosen so that fluid flow through the first andsecond valves is at a constant velocity.

References Cited UNITED STATES PATENTS 1,429,534 9/1922 Renner 261--44 X1,792,053 2/1931 Weidenfeller 261-50 1,913,974 7/1933 Kinby 26150 X2,010,563 3/1935 Ross 261-52 X 2,250,932 7/1941 Kittler 261-51 X2,573,093 10/1951 Burson 261-50 X 2,670,139 2/1954 Phillips.

HARRY B. THORNTON, Primary Examiner.

FRANK W. LUTTER, Examiner. T. R MILES, Assistant Examiner.

1. A MIXING CHAMBER OF A CARBURETTOR HAVING A MAIN JET AND ACOMPENSATING JET FOR THE SUPPLY OF COMBUSTION FUEL, SPACED FROM ONEANOTHER WITH THEIR AXES LYING IN A SINGLE PLANE EXTENDING LONGITUDINALLYWITHIN AND BISECTING THE CHAMBER, THE COMPENSATING JET BEING LOCATEDDOWNSTREAM OF THE MAIN JET, AND HAVING A THROTTLE VALVE COMPRISING TWOPLATES PIVOTALLY ATTACHED TO OPPOSED WALLS OF A PORTION OF THE MIXINGCHAMBER RECTANGULAR IN SECTION, MEANS BEING PROVIDED FOR PIVOTING SAIDTWO PLATES IN SYNCHRONISM WITH ONE ANOTHER TO MOVE THEM FROM A FIRST OROPEN POSITION IN WHICH EACH PLATE LIES ALONG THE RESPECTIVE WALL OF THERECTANGULAR SECTION PORTION TO WHICH IT IS PIVOTALLY ATTACHED TO ASECOND POSITION IN WHICH THE DOWNSTREAM TIPS OF THE PLATES ARE CLOSEDTOGETHER JUST DOWNSTREAM OF THE COMPENSATING JET, AND WHEREIN THE FACINGFACES OF THE PLATES ARE CURVED TO ASSIST IN DIRECTING ANY FLOW OF FLUIDBETWEEN THE TWO PLATES WITH A MINIMUM OF TURBULENCE.